Multimeters are used for measuring a variety of parameters associated with electrical circuitry, such as currents, voltages, resistance and capacitance. A multimeter can be a handheld device useful for basic fault finding and field service work or a sophisticated bench instrument that can measure with a very high degree of accuracy. The instrument may be implemented with an analog meter deflected by an electromagnet or with a digital display such as an LCD (liquid crystal display) screen. While older analog multimeters might have basic accuracies of 5-10%, modern portable digital multimeters, or DMMs, may have accuracies up to ±0.025%.
Multimeters commonly include rotary switches configured such that each rotated position of the rotary switch indicates a different measuring function. For example, a rotary switch on a conventional multimeter may be configured such that a first position corresponds to a voltage measurement, a second position corresponds to a current measurement, and a third position corresponds to a resistance measurement. In this manner, a single instrument can act as a voltmeter, an ammeter, or an ohmmeter by simply rotating a switch.
Since modern digital multimeters provide far more functionality than just three measurement types, rotary switch interfaces have been devised such that a single rotary switch position can be toggled between several measuring functions. As examples, a single position of a rotary switch may correspond to different units of measurement, such as Amps (“A”) or milliamps (“mA”), or even different measurement types altogether, such as a current measurement or a temperature measurement. Typically, the multimeter provides capability on the switch itself or on a function key to toggle between the different measurement functions within the single rotary switch position.
Another feature found in modern digital multimeters enables a user to select between different modes that affect what or how measurements are acquired, maintained or displayed. For example, a user can select a “Minimum/Maximum” mode, which updates the display with the highest and lowest detected measurement values. As another example, a user can select to “Record” a measurement value for memory storage and later retrieval.
Accordingly, digital multimeters incorporate various tools for performing different types of measurements and different capabilities for displaying measurement values in a digital format on a screen. Further capabilities and improvements are needed, however, in both hardware and software, to enable users to organize measurement information to be obtained by the instrument so as to operate the instrument efficiently, effectively, and safely.